I would like to see an option to fill part voids with infill, instead of support material.

I work on a lot of components for RC aircraft. It's sometimes difficult to find the right strength to weight ratio. It would be nice to be able to design a structure with internal voids with the ability to print the structure 100% solid, and the voids as an infill pattern.

Consider the component below. A 90° bend. This piece has a completely solid exterior. The interior has a framework designed through it for added strength. The remaining areas are void. (Top view, Mid-section)

If I were to print this piece at 100% infill, the structure would be solid and the voids would be full of support material. If I had the option to "fill voids with infill" or "print support material as infill" (Along with a Trackbar to spec the void infill percentage) I would imagine the piece could look like this. (Top view, mid section)

I'm sorry if that part isn't the best example. I threw it together really quick.

How would this be any different than using support material with 0 top/bottom separation layers and 0 horizontal offset? You could set the support material fill percentage the same way you could set the infill percentage.